Corrosion resistant electrically conductive thread compound



July 10, 1956 R. J. STEGEMEIER ETAL 2,754,266

CORROSION RESISTANT ELECTRICALLY CONDUCTIVE THREAD COMPOUND Filed Oct. 29, 1953 II- III INVENTORS. flay/{p Jfffl'i/ili/ii, By #4444 M Fun 1,

iinited States Patent CORROSION RESISTANT ELECTRICALLY CONDUCTIVE THREAD COMPOUND Richard J. Stegemeier, Fullerton, and Paul W. Fischer, Whittier, Caiifi, assignors to Union Oil Company of California, Los Angeles, Calif., a corporation of California Application Gctober 29, 1953, Serial No. 389,032

13 Claims. (Cl. 252-19) This invention relates to a pipe thread compound having the usual characteristics of effectively sealing pipe joints, preventing galling or stripping of threads and preventing seizure and also having anticorrosion characteristics together with exceptional electrical conductance.

In many instances it is desirable to use a string of pipe, such as oil well pipe or oil well casing as a conductor for electricity. This use may be in connection with oil well heaters of the electrical type or in connection with electrical logging devices which may be employed during the drilling operations of oil wells. It is found that the usual pipe thread compounds which are capable of preventing metal to metal contact are generally poor conductors of electricity and thus when the ordinary compounds are used in the joints of well tubing, casing and the like, the electrical resistance built up in a long string of tubing, casing, etc., is great enough that it is difficult to operate electrical equipment in or near the bottom of a well using the tubing and/or casing as electrical conductors.

It has been found that by using compositions such as those described hereinbelow as pipe thread compounds the pipe joints are effectively sealed and thus do not leak at relatively high pressures even at temperatures which may exist in oil wells, the joints are protected against corrosion and the application of these compounds permits easy makeaup and break-out of the joints without gelling, stripping and the like. Moreover, these compounds have very low electrical resistance in comparison with ordinary pipe thread compounds and thus when they are used as the thread compounds long strings of pipe may be employed as electrical conductors without the usual power losses.

An object of this invention is to provide a corrosion resistant, electrically conductive thread compound which has the other properties and characteristics usually considered essential in pipe thread compounds.

Further objects of the invention will be readily apparent as the description proceeds.

It has been found that a thread compound consisting essentially of sodium petroleum sulfonate in mineral lubricating oil, containing relatively small amounts of finely divided particles of oxides, metal sulfides or the like, with or without the use of graphite and together with minor but critical amounts of water, have the properties described hereabove. Thus, thread compounds of this composition have been found to possess extremely good conductivity, they are corrosion resistant and thus prevent corrosion of ferrous metal parts with which they are in contact, they permit making-up and breaking-out of pipe joints without galling, welding, stripping, etc., and they form seals which prevent leakage at relatively high pressures and temperatures.

In preparing the thread compounds of this invention, commercial sodium petroleum sulfonate, which generally contains between about 40% and about 70% by weight of sodium petroleum sulfonate and about 26% by weight of water in mineral lubricating oil, is'mixed with between about 0.5% and about 10% and preferably with between about 1% and about 7% by weight based on the total composition of finely divided metal, metal oxide, metal sulfide and/or graphite, and with between about 1% and about 9% by weight and pref= erably between about 2% and about 7% by weight of water based on the total composition depending upon the amount of water present in the petroleum sulfonate. The mixing may be accomplished at ordinary temperatures and once mixed the product does not separate, i. e., the metallic or other solid particles do not settle, nor does the water separate under ordinary or reasonable conditions of storage or handling.

Apparently, the percentage of water in the above composition is critical. Thus, with less than about 5% of water or with more than about 13% of Water in the finished composition, the conductivity of the resulting compound is very low as compared with similar compositions containing between these amounts of water. Preferably the amount of water will be between about 5% and about 12% by weight of the final composition. In addition to the efl ect of increasing conductivity, the water appears to serve as a stabilizing agent and thus prevents the separation or settling of the particles of metal or metal oxide from the compound.

The method which has been used for determining conductivity of thread compounds is to place the compound between electrodes of a given area (0.0434 square inch) and so arranged that the thickness of the film of thread compound between the electrodes may be varied from approximately 0.001 inch to approximately 0.01 inch. This unit, which will be referred to hereinafter as the cell, is arranged in series with a 5000 ohm resistor and 60 cycle alternating current supplied to the system by means of a 6.3 volt filament transformer. Because of the fact that line voltages were generally greater than volts, voltages shown in the table presented hereinbelow are greater than the 6.3 which would nominally be supplied by such a filament transformer operating on 110 volt A. C. current. Alternating current was employed in order to avoid polarization of the electrodes.

In making a given determination, the thread compound to be tested is placed between the electrodes in the cell and a fixed spacing of electrodes employed. The voltage drop across the 5000 o resistor is then determined using a high impedance volt meter and the current, I, calculated from the following equation:

132 where E2 is the voltage drop across the cell and I is the current as determined from the preceding equation. From the resistance, R2 determined in this manner, the specific resistance or resistivity expressed in ohm/centimeters is readily calculated. Since, the conductivity is the reciprocal of the resistivity this value is also readily calculated. Conductivity is expressed in MHO c mf The criticalness of the water content of the thread compounds is readily seen by a reference to the accompanying drawing, which presents three curves showing the relationship between the total water content and the conductivity of typical compositions of this invention,

Referring particularly torthe drawing, all of the data were obtained with an electrode spacing in the cell of 0.005 inch. This value was chosen since the spacing is great enough to prevent direct short through metallic particles present in the compound and yet the spacing approaches the spacing between threads at pipe joints. In the drawing, curve 1 shows the conductivity of a thread compound consisting of a commercial sodium petroleum sulfonate composed of 62% sodium sulfonate, 5% Water and 33% mineral oil, containing 5% copper, based on the finished composition in the form of'powder having a maximum particle size of approximately 0.001 inch and various percentages of added water. The Water contents shown in the drawing are total water contents. It will be noted that with less than about 5% and with more than about 1213% by weight of water the conductivity is extremely poor, as compared with the conductivity of the compound containing from about 5% to about 12- 13% by weight of water.

Curve 2 shows similar data for a composition prepared with the same commercial sodium sulfonate and containing 1% by weight of copper powder of the particle size indicated above with various proportions of water.

Curve 3 shows the conductivity of a thread compound similar to that represented by curve 2 except that 1% by weight of carboxy methyl cellulose was employed as a dispersing agent.

The above curves, which are typical of the curves obtained using other alkali metal sulfonates, e. g., potassium and lithium and other powdered solids as set forth hereinbelow, show the criticality of the water content of the pipe thread compounds of this invention.

Data regarding the actual compositions and the conductivities of the thread compounds shown in the drawing are as follows:

Table 1 Composition, Percent by Weight Water Na Sulionate Oil Copper CMC' I Carboxy methyl cellulose. b Measurements made with an electrode spacing of 0. 004 inch. 0 This point not shown in drawing.

Although the conductivity data were obtained at an electrode spacing of 0.004 inch similar data were obtained with electrode spacings of 0.003 and 0.008 inch indicating that the vehicle itself is conductive.

Solid powdered, flaked, etc., materials which may be employed in place of copper and which give pipe thread compounds having all of the useful characteristics including the high conductivities observed with the compounds prepared with copper, zinc, lead, tin, molybdenum, cobalt, nickel, silver, etc., the corresponding metal oxides and metal sulfides, such as for example, copper oxide or sulfide, zinc oxide, lead oxide, lead sulfide and the like. The mentioned metals, which may be used in the form of the metal itself or in the form of the metal oxide or metal sulfide, are all heavy metals. Graphite may be employed in place of or in combination with metals and/ or metal oxides or sulfides. The metals, metal oxides and metal sulfides must be finely divided, however the shape of the particles does not appear to be critical. The maximum particles size should be less than about 0.002 inch, and preferably it will be less than about 0.001 inch.

Although sodium petroleum sulfpnate in mineral oil has been shown to be the base for the thread compounds described hereinabove, it is to be pointed out that similar results are obtained using potassium petroleum sulfonates and lithium petroleum sulfonates in place of the sodium petroleum sulfonates.

In addition to the sodium petroleum sulfonate, powdered solid material and water, it is sometimes desirable to add small amounts, as for example 0.5% to 5%, of an agent which tends to improve the stability of the compound and aids in preventing the metal, metal oxide or metal sulfide particles from settling. Such additional compounds include carboxy methyl cellulose, sodium polyacrylate and alkylol coconut amides.

For purposes of comparison with the thread compounds of this invention conductivity tests have been made on three commercial thread compounds which consisted of an oleaginous base or vehicle containing powdered or finely divided metal alone or with graphite. In these tests it was observerd that in each case the conductivity of the compound was substantially nil at electrode spacings of 0.010.006 inch and greater, and that as the electrode spacing was reduced the conductance was infinite, due to direct shorting through the metal particles present in the composition. Apparently, in each instance, the oleaginous vehicle showed a complete lack of ability to conduct electricity.

As further representative examples of this invention a compound containing 55.5% sodium sulfonate, 34.3% mineral oil, 8.2% water and 2.0% powdered lead of a maximum particle size of 0.002 inch has a conductivity of 6.5 Xl0- Moreover, a compound of the same composition containing 2.0% by weight of zinc sulfide in place of powdered lead has the same conductivity. With each of the above compounds when the water content was below about 5% or above about 13% by weight the confollowing proportions.

Table I I Percent by Weight Broad Practical Range Range In addition as indicated hereinabove the final compositions may contain dispersing agents such as carboxy methyl cellulose in amounts ranging from about 0.5% to 5%. a

In the above table the alkali metal petroleum sulfonate refers to an alkali metal salt of oil-soluble petroleum sulfonic acids. These acids are generally referred to as mahogany sulfonic acids. The mineral oil is a petroleum oil of lubricating oil grade. The source of this oil is gen erally the commercial sodium or other alkali metal sulfonate, however, it is feasible to add additional quantities of oil to the commercial sulfonate in order to increase the oil to sulfonate ratio. -In such case a lubricating oil or lubricating oil distillate may be-used.

The powdered solid referred to is preferably a metal powder but may be a powdered oxide or sulfide as described hereinabove and may consist in part or wholly of graphite.

With compositions of this invention there is generally only a relatively small change in conductivity with electrode spacings of between about 0.01 and 0.002 inch. Under any circumstance the conductivities are of the same order of magnitude and it is believed that the conductivity of these compositions does not depend on the metal content but rather on the sulfonate-oil-water system or vehicle. This interpretation is substantiated by the fact that a thread compound prepared without metal, metal oxide or metal sulfide but containing about 9% water, 32.7% oil and 58.3% sodium sulfonate has a conductivity of about 6X10- The powdered solids which are used do improve other characteristics of the thread compound. Thus they aid in preventing galling, stripping, etc., of the pipe threads.

The compositions of this invention have been evaluated for corrosion resistance and have been found to prevent corrosion of ferrous metal surfaces with which they are in contact, both in the presence and absence of moisture over periods of several months. Moreover, the torques required to make-up and to break-out pipe joints in which the thread compounds of this invention are employed are no greater, and in some instances, less than the torques required to make-up and break-out similar joints, using pipe thread compounds available commercially. Furthermore, it has been found that the conductivity of strings of pipe, the joints of which have been made up with compositions of this invention, as would be expected from conductivity measurements described hereabove, have extremely low resistance as compared with corresponding strings of pipe made up with commercially available pipe thread compounds.

We claim:

1. A pipe thread compound comprising between about 45% and about 65% by weight of an alkali metal pe troleum sulfonate, between about 13% and about 49.5% by weight of mineral oil, between about 5% and about about 10% by weight of a powdered solid material of 13% by weight of water and between about 0.5 and particle size less than about 0.002 inch, said powdered solid material being selected from the class consisting of powdered heavy metals and powdered oxides and sulfides of heavy metals.

2. A pipe thread compound according to claim 1 in which said alkali metal petroleum sulfonate is sodium petroleum sulfonate.

3. A pipe thread compound according to claim 1 in which said alkali metal petroleum sulfonate is potassium petroleum sulfonate.

4. A pipe thread compound according to claim 1 in which said alkali metal petroleum sulfonate is lithium petroleum sulfonate.

5. A pipe thread compound according to claim 1 in which said powdered solid is copper.

6. A pipe thread compound according to claim 1 in which said powdered solid is lead.

7. A pipe thread compound according to claim 1 containing also between about 0.5 and about 5% of carboxy methyl cellulose.

8. A pipe thread compound consisting essentially of between about and about by weight of alkali metal petroleum sulfonate, between about 20% and about 44% by weight of mineral oil, between about 5% and about 12% by weight of Water and between about 1% and about 8% by weight of powdered heavy metal having a particle size less than about 0.002 inch.

9. A pipe thread compound according to claim 8 containing also between about 0.5% and about 5% of a dispersing agent selected from the class consisting of carboxy methyl cellulose, sodium polyacrylate and alkylol coconut amides.

10. A pipe thread compound according to claim 9 in which said dispersing agent is carboxy methyl cellulose.

11. A pipe thread compound according to claim 8 in which said alkali metal petroleum sulfonate is sodium petroleum sulfonate.

12. A pipe thread compound according to claim 8 in which said powdered metal is copper.

13. A pipe thread compound according to claim 8 in which the particle size of said powdered metal is less than about 0.001 inch.

References Cited in the file of this patent 

1. A PIPE THREAD COMPOUND COMPRISING BETWEEN ABOUT 45% AND ABOUT 65% BY WEIGHT OF AN ALKALI METAL PETROLEUM SULFONATE, BETWEEN ABOUT 13% AND ABOUT 49.5% BY WEIGHT OF MINERAL OIL, BETWEEN ABOUT 5% AND ABOUT ABOUT 10% BY WEIGHT OF A POWDERED SOLID MATERIAL OF 13% BY WEIGHT OF WATER AND BETWEEN ABOUT 0.5% AND PARTICLE SIZE LESS THAN ABOUT 0.002 INCH, SAID POWDERED SOLID MATERIAL BEING SELECTED FROM THE CLASS CONSISTING OF POWDERED HEAVY METALS AND POWDERED OXIDES AND SULFIDES OF HEAVY METALS. 